As mobile communication technology develops the number of frequency bands on which data can be transmitted continues to increase. As of 3GPP Release 11 there are many frequency band allocations defined which can be used for transmission and/or reception of data using frequency division duplexing (FDD) or time division duplexing (TDD). The frequency of the uplink portion, downlink portion and available bandwidth vary for each frequency band allocation. Although it is possible to provide an antenna which will operate across these frequency bands, band specific frequency selective filtering is required for component carriers.
Carrier Aggregation (CA) allows higher data rates by transmitting and/or receiving data over two or more carriers. The carriers can in general be in the same or different frequency band allocations. Furthermore, two or more carriers may be at same frequency.
It is desirable for a wireless device to operate across as many frequency bands as possible to improve its compatibility with different operators and geographical areas. The design becomes challenging as the number of frequency bands and combinations for CA increase. A more complicated switching arrangement typically increases insertion loss and reduces apparatus performance. Insertion loss is the loss in power due to the insertion of a component into the signal path. Strict constraints can be placed on the wireless device performance by network operators, and it can be difficult to meet these constraints as the number of bands and band combinations for CA continue to increase. For example, network cell locations are planned according to devices that are not CA capable. When CA capable devices are used, the impact of the insertion loss introduced by the components to allow CA reduces the operational range. Re-planning cell locations to account for the reduced range of CA capable devices would introduce large costs.
US-2004/0239442A1 discusses a quad band antenna interface. A diplexer is permanently provided in the signal path of all four bands to allow multiplexing of high and low frequency signals through a single antenna. The diplexer provides a permanent insertion loss penalty. WO-2012/109262A discusses a method of improving insertion loss in a multi-band device. A bypass switch is provided to route uplink signals around a multiplexer when the device is operating in single band mode, reducing the uplink insertion loss in single band mode.
The same reference number is used to indicate the same part throughout the drawings.